Patients with neuromuscular weakness as a result of strokes, spinal cord injuries, head trauma, or diseases such as muscular dystrophy and amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease) have an increased risk of morbity and mortality due to a weak cough and shallow breathing (hypoventilation). The number of chronic illnesses that cause weak cough and impaired lung ventilation is large and expanding.
When a patient has an ineffective cough, chest secretions are retained in the respiratory system, causing pneumonia, lung collapse, or, where the mucus fills the windpipe, fatal respiratory arrest. Additionally, shallow breathing causes low oxygen levels and high carbon dioxide levels in the patient's bloodstream, resulting in a medically fragile state of chronic respiratory failure in which even a common cold can result in severe respiratory illness. For these reasons, pulmonary complications are viewed as a major cause of morbidity and death in patients that have neuromuscular weakness.
As a patient's condition worsens, it becomes more likely that the patient will need both cough assistance and assisted ventilation. Respiratory therapies for addressing a weak cough often involve devices that provide assisted coughing via mechanical insufflation/exsufflation, while shallow breathing is commonly addressed by a separate, mechanical ventilation device.